A Role for Pom121 in Linking the Nuclear Pore Complex Membrane Scaffold to the Pore Membrane Domain

  • Author / Creator
    Mitchell, Jana M
  • A key step in the evolutionary progression from prokaryote to eukaryote was development of the endomembrane system, including encapsulation of genetic material by the impermeable nuclear envelope (NE). Trafficking of macromolecules between cytoplasmic and nuclear compartments required the concomitant evolution of nuclear pore complexes (NPCs), sophisticated transport channels embedded within the NE. NPCs are comprised of a highly specialized subset of proteins termed nucleoporins (Nups). Nups that localize to the pore membrane domain (POM) of the NE stabilize membrane curvature resulting from circumferential fusion of NE membrane leaflets to form the pore in which the NPC resides. The architecture of the membrane-scaffolding NPC coat, and importantly, how this coat interfaces the POM, is unknown. We examined the interactions between NPC scaffold proteins Nup155 and Nup160 with the POM. We show that depletion of Nup155 causes alterations in NE structure, including a dramatic decrease in NPC numbers. We describe novel interactions between β-propeller domains of Nup155 and Nup160 with the transmembrane Nup (Pom) Pom121, and suggest that these interactions are critical for NPC assembly. To better define a role for scaffold Nups in NPC structural organization, we focused on determining atomic structures of Nups comprising the conserved Nup107-160 scaffold complex. We present the crystal structure of the Schizosaccharomyces pombe (Sp) Nup1201-950-Nup37 heterodimer (orthologous to metazoan Nup160 and Nup37), and demonstrate that capture of Nup37 within the  scaffold coat co-evolved with the acquisition of an α-helical domain within the β- propeller of Nup160 orthologues. We demonstrated that this interaction is conserved in metazoan cells, and extended our analysis to investigate the association of additional scaffold β-propellers with Pom121. We uncovered novel interactions between Pom121 with Nup37 and Nup43, expanding the Pom121 interactome to include four β-propeller proteins of the NPC membrane coat. We envisage a model whereby Pom121 extends from the NE towards the NPC central channel, linking structural modules of the NPC through interactions with β- propeller domains of Nup37, Nup43, Nup155 and Nup160. These interactions are likely regulated during NPC assembly, and plasticity of the Pom121 interactome may facilitate the reversible dilation of the NPC transport channel in response to cellular metabolic demands.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Cell Biology
  • Supervisor / co-supervisor and their department(s)
    • Wozniak, Rick (Cell Biology)
  • Examining committee members and their departments
    • Melancon, Paul (Cell Biology)
    • Chook, Yuh Min (Pharmacology, Biophysics)
    • Monpetit, Ben (Cell Biology)
    • Underhill, Alan (Oncology)